VOLVO
ECM-1834 - Relay, engine coolant heater 1. Signal too low
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsS40 (1996–2004), V40 (1996–2004)
Show models by year and engine (2)
What does this fault code mean?
The engine control module (ECM) has detected that the control signal to the relay for engine coolant heater 1 is too low. The relay switches the electric coolant heater in the cooling system, which helps the engine warm up in cold weather. The fault is usually caused by an open circuit or a short to ground in the control wire, but a defective relay can also trigger the code.
Possible causes
- Open circuit in the control wire to the relay
- Control wire short-circuited to ground
- Defective relay for engine coolant heater 1
What you can do
- 1Read and clear the fault code, road test and see whether it returns
- 2Check that the fuse for the coolant heater relay is intact
- 3Check that the relay sits firmly in the fuse and relay box in the engine compartment and that its contacts are clean
- 4Use a multimeter to check that the control wire has no open circuit and no contact with ground (body)
- 5If you have a diagnostic tool, activate the coolant heater relay and listen for it to click
Symptoms you may notice1
- No noticeable symptoms for the driver
What the fault can affect1
- The control module uses a fixed value instead of the signal from the relay
General guidance for car owners. Diagnosis on the car can point to a different cause.